Is WHMCS SMTP error could not authenticate troubling you? We can help you with it.

Usually, this error occurs due to incorrect SMTP settings.

At Bobcares, we often receive requests to resolve these errors as part of our Server Management Services.

Today, let’s have a deep look at this error and see how our Support Engineers fix it easily.

Why do WHMCS SMTP error could not authenticate occur?

Isn’t it really frustrating to get error messages while sending important mails?

Usually, when such error occurs, we navigate to Utilities > Logs > Activity Log. And, we review the logs for the error message that occurred at the time of email sending.

Sometimes, the problem could be an authentication error due to incorrect SMTP settings.

An authentication error happens when the mail server rejects the provided SMTP details.

How we fix this SMTP could not authenticate error?

So, for getting more detailed information about the error, we usually add the below line to the configuration.php file,

$smtp_debug = true;

And, this will give a lot of debugging information regarding the error that has occurred while sending the email.

1. Incorrect SMTP settings

Sometimes, the general SMTP settings like port, host, username, password, etc stored in Setup > General Settings > Mail tab, maybe given incorrectly.

In such cases, the mail server blocks connections from the server upon which WHMCS has been installed.

So, in order to resolve the error, we need to make sure that we have provided the correct SMTP details.

Similarly, this error also occurs when an inappropriate SMTP port has been specified for use with the SSL Type option selected.

For instance, selecting SSL and port number 25 will cause this error.

2. SMTP restrictions

Recently, one of our customers approached us with a WHMCS SMTP error. He was getting authentication error messages whenever he tried to send emails.

Our Support Engineers checked the error in detail and found SMTP restrictions problem in it.

SMTP restrictions in WHM allow configuring the server so that only the MTA, Mailman mailing list software, and the root user can connect to the remote SMTP server.

And, it will automatically re-route any SMTP traffic leaving the server back to the localhost.

So, we disabled this option in WHM, Home >> Security Center >> SMTP Restrictions. This resolved the error and mail services worked fine.

[Need more assistance to resolve this error?- We’ll help you.]

Conclusion

In short, WHMCS SMTP error could not authenticate occur mainly due to incorrect SMTP settings and SMTP restrictions. Today, we have discussed this error in detail and saw how our Support Engineers fix this error for our customers.